Cerebrospinal fluid metabolomics identifies a key role of isocitrate dehydrogenase in bipolar disorder: evidence in support of mitochondrial dysfunction hypothesis

Although evidence for mitochondrial dysfunction in the pathogenesis of bipolar disorder (BD) has been reported, the precise biological basis remains unknown, hampering the search for novel biomarkers. In this study, we performed metabolomics of cerebrospinal fluid (CSF) from male BD patients (n=54) and age-matched male healthy controls (n=40). Subsequently, post-mortem brain analyses, genetic analyses, metabolomics of CSF samples from rats treated with lithium or valproic acid were also performed. After multivariate logistic regression, isocitric acid (isocitrate) levels were significantly higher in the CSF from BD patients than healthy controls. Furthermore, gene expression of two subtypes (IDH3A and IDH3B) of isocitrate dehydrogenase (IDH) in the dorsolateral prefrontal cortex from BD patients was significantly lower than that of controls, although the expression of other genes including, aconitase (ACO1, ACO2), IDH1, IDH2 and IDH3G, were not altered. Moreover, protein expression of IDH3A in the cerebellum from BD patients was higher than that of controls. Genetic analyses showed that IDH genes (IDH1, IDH2, IDH3A, IDH3B) and ACO genes (ACO1, ACO2) were not associated with BD. Chronic (4 weeks) treatment with lithium or valproic acid in rats did not alter CSF levels of isocitrate, and mRNA levels of Idh3a, Idh3b, Aco1 and Aco2 genes in the rat brain. These findings suggest that abnormality in the metabolism of isocitrate by IDH3A in the mitochondria plays a key role in the pathogenesis of BD, supporting the mitochondrial dysfunction hypothesis of BD. Therefore, IDH3 in the citric acid cycle could potentially be a novel therapeutic target for BD.

Impact force measurement of a spherical body dropping onto a water surface

We propose a method for measuring the impact force of a spherical body dropping onto a water surface. The velocity of the center of gravity of a metal spherical body, in which a cube corner prism is embedded so that its optical center coincides with the center of gravity of the sphere, is accurately measured using an optical interferometer. The acceleration, displacement, and inertial force of the sphere are calculated from the velocity. The sphere is also observed using a high-speed camera. The uncertainty in measuring the instantaneous value of the impact force with a sampling interval of approximately 1 ms is estimated to be 8 mN, which corresponds to 0.8% of the maximum force of approximately 1.0 N.

Neurite outgrowth mediated by the heat shock protein Hsp90α: a novel target for the antipsychotic drug aripiprazole

Aripiprazole is an atypical antipsychotic drug approved for the treatment of psychiatric disorders such as schizophrenia, bipolar disorder, major depressive disorder and autism. The drug shows partial agonistic activity at dopamine D(2) receptors and 5-hydroxytryptamine (5-HT) 5-HT(1A) receptors, and antagonistic activity at 5-HT(2A) receptors. However, the precise mechanistic pathways remain unclear. In this study, we examined the effects of aripiprazole on neurite outgrowth. Aripiprazole significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration-dependent manner. The 5-HT(1A) receptor antagonist WAY-100635, but not the dopamine D(2) receptor antagonist sulpiride, blocked the effects of aripiprazole, although, only partially. Specific inhibitors of inositol 1,4,5-triphosphate (IP(3)) receptors and BAPTA-AM, a chelator of intracellular Ca(2+), blocked the effects of aripiprazole. Moreover, specific inhibitors of several common signaling pathways phospholipase C-γ (PLC-γ), phosphatidylinositol-3 kinase (PI3K), mammalian target of rapamycin, p38 MAPK, c-Jun N-terminal kinase, Akt, Ras, Raf, ERK, MAPK) also blocked the effects of aripiprazole. Using proteomic analysis, we found that aripiprazole significantly increased levels of the heat shock protein Hsp90α in cultured cells. The effects of aripiprazole on NGF-induced neurite outgrowth were significantly attenuated by treatment with Hsp90α RNA interference, but not by the negative control of Hsp90α. These findings suggest that both 5-HT(1A) receptor activation and Ca(2+) signaling via IP(3) receptors, as well as their downstream cellular signaling pathways play a role in the promotion of aripiprazole-induced neurite outgrowth. Furthermore, aripiprazole-induced increases in Hsp90α protein expression may form part of the therapeutic mechanism for this drug.

Results after 24 years of prophylactic surgery for rheumatoid atlantoaxial subluxation

We evaluated the use of surgical stabilisation for atlantoaxial subluxation after a follow-up of 24 years in 50 rheumatoid patients who had some degree of pain but no major neurological deficit.

The mortality of patients treated by atlantoaxial fusion was significantly lower than for those who received conservative treatment. The deaths resulted from infection or comorbid conditions. The significantly high relative risks of mortality from conservative treatment compared with surgical treatment were mutilating disease and susceptible factors on both of the HLA-DRB1 alleles. Relief from pain and neurological and functional recovery were better, and the radiological degree of atlantoaxial translocation was less in those who were surgically treated compared with those who were not. Two patients had superficial local infections after surgery. We conclude that prophylactic atlantoaxial fusion is better than conservative treatment in these patients.

Timing of the administration of tranexamic acid for maximum reduction in blood loss in arthroplasty of the knee

We studied 99 patients who were undergoing total knee arthroplasty (TKA) to determine the optimum protocol for the administration of tranexamic acid (TNA) in order to reduce blood loss. It decreased by more than 40% after the administration of TNA. The haemostatic effect was greatest when TNA was given preoperatively and on deflation of the tourniquet. There was no increase in the incidence of adverse affects in the patients receiving TNA, compared with a control group.

We conclude that two injections of TNA, one given preoperatively and one on deflation of the tourniquet, significantly reduce blood loss without increasing the risk of thromboembolic complications.

Timing of the administration of tranexamic acid for maximum reduction in blood loss in arthroplasty of the knee

We studied 99 patients who were undergoing total knee arthroplasty (TKA) to determine the optimum protocol for the administration of tranexamic acid (TNA) in order to reduce blood loss. It decreased by more than 40% after the administration of TNA. The haemostatic effect was greatest when TNA was given preoperatively and on deflation of the tourniquet. There was no increase in the incidence of adverse affects in the patients receiving TNA, compared with a control group. We conclude that two injections of TNA, one given preoperatively and one on deflation of the tourniquet, significantly reduce blood loss without increasing the risk of thromboembolic complications.

A mechanistic study of reactions of stable disilenes with haloalkanes

Mechanisms of the reactions of three tetrakis(trialkylsilyl)disilenes and a tetraaryldisilene with various haloalkanes such as carbon tetrachloride, chloroform, dichloromethane, which gave the corresponding 1-alkyl-2-chlorodisilanes and/or 1,2-dichlorodisilanes, were investigated in detail. As evidenced by an ESR observation of an intermediate radical, these reactions were quite unusual, forming neutral radical pairs from two closed shell molecules at the first step; no similar reactions have been observed between alkenes and haloalkanes. Low oxidation potentials of these disilenes, large negative activation entropies, and solvent effects for the rates are in good accord with the direct halogen abstraction of disilenes from haloalkanes instead of single-electron transfer at the rate-determining first step. The structure--reactivity relationship of the reactions and the Hammond postulate suggest that the transition state structures for the first step are similar to those for the halogen abstraction by silyl radicals, but more product-like.

[Isolation of Legionella and free-living amoebae at hot spring spas in Kanagawa, Japan]

Microbiological contamination of hot spring bath water is a public health concern. A province-wide survey was carried out to determine the extent and distribution of both Legionella and free-living amoebae contamination. Among 30 samples of hot spring bath from 12 sites in Kanagawa, Japan, L. pneumophila was detected in 21 water samples from 11 sites, ranging from 10(1)-10(3) CFU/100 ml. Serogroups 3, 5 and 6 of L. pneumophila were predominantly isolated from the samples. Naegleria (46.7%), Platyamoeba (33.3%), Acanthamoeba (10.0%) and 2 other genera of free-living amoebae were detected in 22 samples from 11 sites. One or more genera of host amoebae of Legionella occurred in 17 samples (56.7%) from 9 sites. Another thing to be noted is that 13 water samples contained N. lovaniensis. Although N. lovaniensis is nonpathogenic, it is considered an indicator organism for places that are suitable for the growth of N. fowleri, a causative agent of primary amoebic meningoencephalitis in man.

The 5-HT3 receptor agonist attenuates the action of antidepressants in the forced swim test in rats

Involvement of 5-hydroxytryptamine (5-HT)3 receptors in action of antidepressants was examined in the forced swim test in rats. Rats were forced to swim in a cylinder for 15 min on day 1 and for 5 min on day 2. Imipramine, desipramine and mianserin, administered after the 15-min swim session on day 1 and before the 5-min swim test on day 2, dose-dependently decreased the duration of immobility in the swim test on day 2. 1-(m-Chlorophenyl)-biguanide (mCPBG) attenuated the decreased duration of immobility induced by imipramine, desipramine and mianserin, although mCPBG did not affect the duration of immobility when it was given alone. ICS205-930 dose-dependently decreased the duration of immobility in the swim test on day 2, and the effect of ICS205-930 was attenuated by mCPBG. These results suggest that the suppression of 5-HT3 receptor activity may contribute to the action of antidepressants.

Effect of a novel cognition enhancer NS-105 on learned helplessness in rats: possible involvement of GABA(B) receptor up-regulation after repeated treatment

We have previously found that a cognition enhancer [(+)-5-oxo-D-prolinepiperidinamide monohydrate] (NS-105) reversed the inhibition of cyclic AMP formation induced by the GABA(B) receptor agonist baclofen. The GABA(B) receptor has been implicated in the pathophysiology of depressive illness. The present experiment was designed to evaluate the antidepressant activity of NS-105 in the forced swimming and learned helplessness tests in rats. NS-105 (1-100 mg/kg, p.o.) significantly decreased immobility time in the forced swimming test, an effect similar to that of desipramine. Repeated administration of NS-105 also reversed the failure to escape in the shuttle-box test of rats previously exposed to inescapable footshock. Biochemical data showed that repeated administration of NS-105 increased the number of GABA(B) receptors in rat cerebral cortex without affecting the binding properties of beta-adrenoceptors and 5-HT2 receptors. In contrast to other antidepressants, NS-105 did not inhibit monoamine uptake in vitro, nor did it change monoamine concentrations in brain tissues or extracellular fluids. These findings suggest that NS-105, which lacks an effect on monoaminergic systems, has potent antidepressant activity, which may involve up-regulation of GABA(B) receptors after repeated administration.

Involvement of GABAB receptor systems in experimental depression: baclofen but not bicuculline exacerbates helplessness in rats

There are two gamma-aminobutyric acid (GABA) hypotheses of the antidepressants action: an increase in GABAA neurotransmission or a decrease in GABAB neurotransmission may contribute to action of antidepressants. In this study, involvement of GABAA and GABAB receptor systems was examined in the learned helplessness paradigm in rats. Rats were injected with bicuculline or baclofen for 14 days. On day 14, the rats were subjected to 15 inescapable shocks. On day 15, they underwent the 40-trial escape test. Baclofen exacerbated the escape failures in the rats subjected to the inescapable shocks, although baclofen had no effects in the animals without shock pre-treatment. Bicuculline failed to influence the escape failures in the rats with the 15-shock pre-treatment. These results suggest that the long-term increase in GABAB neurotransmission but not the long-term attenuation of GABAA neurotransmission may be related to helplessness in rats.

Involvement of GABAB receptor systems in action of antidepressants. II: Baclofen attenuates the effect of desipramine whereas muscimol has no effect in learned helplessness paradigm in rats

Involvement of GABAergic systems in action of antidepressants was examined in the learned helplessness paradigm in rats. Rats were treated with desipramine, baclofen or muscimol for 14 days. On day 14, the rats were subjected to 90 inescapable shocks. On day 15, the rats received the 40-trial escape test. The inescapable shocks induced the subsequent increase in escape failures in the escape test. Desipramine dose-dependently improved the increased escape failures induced by the inescapable shocks. Baclofen attenuated the escape failures-improving effect of desipramine, although baclofen had no effects on the increased escape failures when it was injected alone. Muscimol at any dose failed to influence the increased escape failures. Therefore, it is suggested that the long-term decrease in GABAB neurotransmission may be involved in the action of antidepressants. Our present results do not support the hypothesis that activation of GABAA receptors may contribute to the action of antidepressants.

Involvement of GABA(B) receptor systems in action of antidepressants: baclofen but not bicuculline attenuates the effects of antidepressants on the forced swim test in rats

Involvement of GABAergic systems in action of antidepressants was examined in the forced swim test in rats. Rats were forced to swim in a cylinder for 15 min on day 1 and for 5 min on day 2. Desipramine, mianserin and buspirone, administered after the 15-min swim session on day 1 and before the 5-min swim test on day 2, dose-dependently decreased the duration of immobility in the swim test on day 2. Baclofen attenuated the decreased duration of immobility induced by desipramine, mianserin and buspirone in the swim test, although baclofen did not affect the duration of immobility when it was injected alone. Muscimol dose-dependently decreased the duration of immobility in the swim test on day 2. Bicuculline antagonized the decreased duration of immobility induced by muscimol. However, bicuculline failed to antagonize the decreased duration of immobility induced by desipramine, mianserin and buspirone. These results suggest that GABA(B) but not GABA(A) receptor systems may be involved in action of antidepressants.

Irsogladine activates gap-junctional intercellular communication through M1 muscarinic acetylcholine receptor

Irsogladine, an agent that protects gastric mucosa against various ulcerogenic stimuli through increasing cyclic AMP in surface mucous cells, has been reported to dose-dependently (10(-7) to 10(-5) M) facilitate gap-junctional intercellular communication (GJIC) in gastric epithelial cells. The beta adrenergic agonist, isoproterenol, stimulates GJIC in resting cells and inhibits GJIC in cells activated by 3-isobutyl-1-methylxanthine. In this study, we investigated whether irsogladine acts on GJIC in a manner similar to that shown by isoproterenol. Irsogladine, which bound to M1 muscarinic acetylcholine receptors (mAChR), did not inhibit, but failed to further facilitate the 3-isobutyl-1-methylxanthine-enhanced GJIC, measured by Lucifer yellow transfer. The enhancement of GJIC by irsogladine was inhibited by the M1 mAChR antagonist, pirenzepine. A selective M1 mAChR agonist, McN-A-343, enhanced GJIC. Isoproterenol (10(-8) to 10(-6) M), which alone did not affect GJIC, inhibited the GJIC enhanced by 10(-5) M irsogladine. Conversely, 10(-10) to 10(-6) M irsogladine, which alone did not affect GJIC, inhibited the GJIC enhanced by 10(-5) M isoproterenol. McN-A-343 also converted the action of 10(-5) M isoproterenol from facilitation to inhibition of GJIC. These results indicate that GJIC is heterologously down-regulated by cross-talk between M1 mAChR and beta adrenergic receptors. In addition, the effects of irsogladine and isoproterenol at low concentrations suggest the involvement of another mechanism for down-regulating GJIC.

Interaction between benzodiazepine and GABA-A receptors in state-dependent learning

State-dependent learning (SDL) induced by benzodiazepine (BDZ) and GABA-A agonists was investigated in the step-through passive avoidance task in rats. Pre-training injection of diazepam or muscimol dose-dependently reduced step-through latency in the test session conducted 24 hr after the training. Injection of either drug before both the training and test sessions, however, failed to reduce the latency. The results show that passive avoidance failures induced by pre-training injections of diazepam and muscimol are due to SDL. In contrast to diazepam and muscimol, baclofen induced no SDL. Diazepam and muscimol were found to substitute for each other in producing SDL. The failure of learning performance in SDL (dissociation in SDL) induced by diazepam was blocked by flumazenil and picrotoxin but not by bicuculline injected before the training session, whereas dissociation in SDL induced by muscimol was blocked by flumazenil, bicuculline and picrotoxin. On the other hand, the success of learning performance in SDL (non-dissociation in SDL) induced by diazepam was blocked by flumazenil, bicuculline and picrotoxin injected before the test session, whereas non-dissociation in SDL induced by muscimol was blocked by bicuculline and picrotoxin but not by flumazenil. These results demonstrate that 1) BDZ and GABA-A agonists produce a common drug state, but, 2) roles of each receptor in SDL might be different, i.e., BDZ receptors for dissociation in SDL and GABA-A receptors for non-dissociation in SDL, and 3) chloride ion channels are essential for the induction of SDL by BDZ and GABA-A agonists.

[A case report of monitoring neuromuscular blockade during anesthesia in a patient with facioscapulohumeral muscle dystrophy]

Facioscapulohumeral muscle dystrophy (FSHMD) is characterized by slowly progressive wasting of facial, pectoral and shoulder-girdle muscles that begins in adolescence. A 31 year-old man with FSHMD had dystrophic changes in the deltoid, anterior serratus and pectoralis major muscles but not in the distal muscle of his arms and legs. He underwent an operation for thoraco-scapula fixation under enflurane-nitrous oxide anesthesia with vecuronium 6 mg. At the end of the surgical procedure, the train-of-four (TOF) responses of a thumb and a toe, as measured by using an acceleration transducer, were recorded simultaneously. TOF stimulation in an arm demonstrated an apparent fade phenomenon (TOF; 0.54), while a TOF test in the leg showed complete recovery of the TOF ratio (TOF; 1.0). The patient revealed no clinical signs of residual neuromuscular blockade. It was clear that there was a difference in the degree of neuromuscular block between the arm and the leg in a FSHMD patient. Use of the peripheral nerve stimulator only in the arm may be an unreliable guide to assess neuromuscular block in FSHMD patients. Therefore, two sites should be chosen for monitoring neuromuscular blockade in a FSHMD patient.

[Pharmacological studies of celiprolol: II. Alpha 2-Adrenoceptor blocking effects of a cardioselective beta-blocker, celiprolol]

alpha-Adrenoceptor blocking effects of the cardioselective beta-blocker celiprolol were tested. 1. Celiprolol antagonized the contractions induced by UK-14304, but not those by phenylephrine, in isolated rat tail arteries with a pA2 value of 4.95. 2. In the isolated rat vas deferens, twitch contractions elicited by the transmural electrical stimulation (TS) were almost blocked by TTX (10(-7) M). Clonidine inhibited the TTX-sensitive contraction in a concentration-dependent manner. Celiprolol produced little effect on the inhibitory effects of clonidine. The concentration-inhibition curve of clonidine was shifted to the right by yohimbine (10(-8) M), but not by prazosin (10(-8) M). 3. Although celiprolol slightly increased the 3H-efflux to TS from the [3H]-norepinephrine-loaded rat vas deferens, the increment was not significant. Yohimbine (10(-7) M) significantly increased the 3H-efflux. TTX (10(-7) M) and bretylium (3 x 10(-5) M) blocked the 3H-efflux. 4. In the spinal rat treated with propranolol (3 mg/kg, i.v.) and prazosin (0.1 mg/kg, i.v.), celiprolol (30 and 100 mg/kg, i.v.) and yohimbine (0.1-1 mg/kg, i.v.) inhibited the pressor response to clonidine. 5. These results indicate that celiprolol may have a weak alpha 2-blocking effect which was more effective on postsynaptic alpha 2-receptors than presynaptic ones.

Density and localization of alpha 1-adrenoceptors in hypertrophied prostate

Alpha-adrenoceptors have been considered to play an important role in the regulation of the voiding force. In order to determine the density and localization of the alpha-adrenoceptors in the prostate, binding assays for alpha-adrenoceptors were performed with [3H]prazosin and [3H] yohimbine in membrane preparations from enucleated hyperplastic prostate tissues. Furthermore, autoradiographic analysis of alpha-adrenoceptors in the sliced tissue specimens from benign prostatic hypertrophy was performed. Specific binding of both ligands were saturable and of high affinity in membrane preparations, and Scatchard analyses indicated Bmax = 104 fmole/mg. protein, Kd = 0.488 nM for [3H]prazosin, and Bmax = 41 fmole/mg, protein, Kd = 1.83 nM for [3H] yohimbine. Bmax and Kd for [3H]prazosin were greater in the adenoma than in the submucosal tissue of the prostatic urethra. No relationship was noted between the size of enucleated prostate and the density of alpha-adrenoceptors. Image analysis of autoradiograms using [3H]prazosin showed specific binding sites could not be clearly demonstrated, but only [125I]HEAT slightly exposed specific binding sites in the prostate.

Developmental changes in beta-adrenoceptors, muscarinic cholinoceptors and Ca2+ channels in rat ventricular muscles

1. In an attempt to explain the previous electrophysiological data on the ontogeny of beta-adrenergic and muscarinic cholinergic interactions on cardiac Ca2+ current, biochemical studies were performed on the ontogeny of beta-adrenoceptors, muscarinic cholinoceptors and Ca2+ channels in cardiac muscle of developing rats: 16-20 days old foetuses, 0-20 days old neonates, and 2-3 months old adults. 2. Developmental changes in cardiac beta-adrenoceptors, muscarinic cholinoceptors, and Ca2+ channels were determined with the use of specific radioligands, [3H]-dihydroalprenolol (DNA), [3H]-quinuclidinyl benzilate (QNB), and [3H]-nitrendipine (NTD), respectively. 3. The Bmax value (fmol mg-1 tissue) for [3H]-DNA binding started to increase on post-gestation day 20, reached almost its maximum level on neonatal day 6, kept almost the same level until neonatal day 20, and then decreased slightly to its adult level. 4. The Bmax value (fmol mg-1 tissue) for [3H]-QNB binding started to increase on post-gestation day 16, reached almost its maximum level on neonatal day 0, remained almost constant until neonatal day 15, and then decreased to its adult level. 5. The Bmax value (fmol mg-1 tissue) for [3H]-NTD binding increased with age between post-gestation day 18 and neonatal day 15, stayed almost constant until neonatal day 20, and then decreased to its adult level. 6. The Kd values for [3H]-DHA, [3H]-QNB, and [3H]-NTD bindings remained almost constant during the developmental period examined. 7. Isoprenaline (Iso) increased the kx of slow action potentials (APs) from post-gestation day 18, and the adult level was reached at about 2 weeks after birth; this developmental time course is similar to that of Ca2+ channels. The number of beta-adrenoceptors also started to increase a few days before birth, but attained its peak about one week earlier than did the Pax of slow APs or the number of Ca2 + channels. 8. Acetylcholine (ACh) almost completely abolished the Iso-induced increase in m,,ax observed from postgestation day 18 to neonatal day 20; this developmental time course for the ACh effect is consistent with the finding that the number of muscarinic cholinoceptors started to increase on post-gestation day 16 and reached a peak on the day of birth. 9. Previous electrophysiological and the present biochemical findings strongly suggest that the functional coupling between muscarinic cholinoceptors and Ca2+ current is already established when the coupling between beta-adrenoceptors and Ca2 + current starts to operate in developing rat hearts.

Muscarinic supersensitivity and subsensitivity induced by chronic treatment with atropine and diisopropylfluorophosphate in rat submaxillary glands

Rats were given atropine for 2 weeks and a cholinesterase inhibitor, diisopropylfluorophosphate (DFP) for 4 weeks. The secretory response of the submaxillary glands to pilocarpine and the muscarinic receptor binding to [3H]quinuclidinyl benzylate (QNB) and [3H]pirenzepine (PZ) in the submaxillary glands were investigated. Experiments were performed 48 and 24 hr after the last administration of atropine and DFP, respectively. Chronic atropine treatment enhanced the secretory response and increased the number of binding sites for [3H]QNB and [3H]PZ. The increase in number of binding sites for the 2 radioligands was almost the same. Chronic DFP treatment caused a marked decrease in the secretory response to pilocarpine, without affecting [3H]PZ and [3H]QNB binding. These results suggest that the cholinergic muscarinic M1 receptors may contribute to the development of the supersensitivity of the salivary glands caused by atropine, but not to the development of subsensitivity caused by DFP.

Specific increase of hypothalamic alpha 1-adrenoceptors in spontaneously hypertensive rats: effect of hypotensive drug treatment

To study potential central adrenoceptor alterations in the hypertension, we have determined alpha 1, alpha 2 and beta-adrenoceptors using [3H]WB4101, [3H]yohimbine and [3H]DHA in the brain regions of spontaneously hypertensive rats (SHR), stroke-prone SHR (SHRSP) and renal hypertensive rats. There was a significant increase in specific [3H]WB4101 binding only in the hypothalamus of SHR and SHRSP at 16-24 weeks of age compared to that of age-matched Wistar-Kyoto rats (WKY). Scatchard analysis revealed a 28-33% increase in the Bmax value for hypothalamic [3H]WB4101 binding without a change in the Kd value, suggesting a change in the receptor density. An increased density of alpha 1-adrenoceptors was consistently observed in the prehypertensive (5 weeks) and developmental (10 weeks) stages of spontaneous hypertension. In contrast, there was no alpha 1-adrenoceptor alteration in the hypothalamus of rats with renal hypertension. The receptor alteration in the SHRSP hypothalamus was not abolished by a chronic hypotensive treatment which prevented the development of hypertension, thereby suggesting that an increased density of the alpha 1-adrenoceptors in spontaneous hypertension does not occur secondarily to the elevation of blood pressure. The SHRSP hypothalamus showed significantly lowered levels of noradrenaline. There was no change in specific binding of [3H]yohimbine and [3H]DHA in the brain regions of SHRSP, except the brainstem which showed a significant decrease in the [3H]yohimbine binding. Thus, the present study suggests an important role for hypothalamic alpha 1-adrenoceptors in the pathogenesis of spontaneous hypertension.

Muscarinic cholinoceptors and choline acetyltransferase activity in the hypothalamus of spontaneously hypertensive rats

To study the role of central cholinergic mechanisms in hypertension, we have determined muscarinic receptors using [3H] (-)quinuclidinyl benzilate (QNB) and choline acetyltransferase (ChAT) activity in the brain regions of spontaneously hypertensive rats (SHR), stroke-prone SHR (SHRSP) and renal hypertensive rats. The number of muscarinic receptors was significantly (33-38 %) elevated in the hypothalamus of SHR and SHRSP at the ages of 16 and 24 weeks compared to that of Wistar-Kyoto rats (WKY). An increased density of muscarinic receptors was consistently observed in the prehypertensive (5 weeks) and developmental (10 weeks) stages of hypertension. In contrast, in the hypothalamus of rats with renal hypertension there was no muscarinic receptor alteration. The receptor alteration in the SHRSP hypothalamus was not abolished by a chronic hypotensive treatment which prevented the development of hypertension, suggesting that an enhancement of the muscarinic receptors in spontaneous hypertension does not occur secondarily to the elevation of blood pressure. The hypothalamus of SHR and SHRSP at the ages of 5 and 24 weeks showed significantly less activity of ChAT. These data demonstrate that there is a specific increase in muscarinic receptors and a decrease in cholinergic activity in the hypothalamus of SHR and SHRSP. Thus, the present study suggests an important role for hypothalamic cholinergic receptors in the pathogenesis of spontaneous hypertension.

Alterations in cardiac alpha and beta adrenoceptors during the development of spontaneous hypertension

To study potential cardiac receptor alterations during the development of spontaneous hypertension, specific binding of [3H]-2-N(2,6-dimethoxyphenoxyethyl)amino-methyl-1,4-benzodioxane, (-)-[3H]dihydroalprenolol and (-)-[3H]quinuclidinyl benzilate in ventricles of Wistar Kyoto rats (WKY), spontaneously hypertensive rats (SHR) and stroke-prone SHR (SHRSP) at different ages was determined. The Kd and maximal binding for specific binding of [3H]-2-N(2,6-dimethoxyphenoxyethyl)amino-methyl-1,4-benzodioxane and (-)-[3H]dihydroalprenolol in ventricular homogenates of SHR and SHRSP at prehypertensive ages were similar to those of age-matched WKY. With the development of spontaneous hypertension in SHR and SHRSP, there was a significant decrease in the maximal binding for both ligands without a change in Kd. The decrease in maximal binding in SHR and SHRSP at 10 weeks of age was 29 to 38%, compared with age-matched WKY. There was no difference in ventricular (-)-[3H]quinuclidinyl benzilate binding between WKY and SHRSP. Hofstee analysis of the inhibition of ventricular (-)-[3H]dihydroalprenolol binding by practolol demonstrated a specific 51% decrease in ventricular beta-1 receptor density in 10-week-old SHRSP. In addition, the inotropic response to isoproterenol in isolated papillary muscles from SHRSP was significantly smaller than that in WKY. Thus, it is concluded that during the development of spontaneous hypertension in SHR and SHRSP, there is a specific loss in number of cardiac alpha and beta-1 adrenoceptors with a consequently reduced responsiveness of isolated papillary muscles to isoproterenol in SHRSP. These results are compatible with the reported increase in sympathetic outflow to the cardiovascular system in spontaneous hypertension.